Innate immune responses to viruses and other pathogens typically involve a highly conserved host-cell signaling mechanism designed to protect and rid the host of harmful microbes. Recognition of conserved microbial structures is initiated by pattern recognition receptors (PRRs), which subsequently induce signaling cascades resulting in the production of cytokines and type-l interferons. Thus far, three families of PRRs have been shown to be activated in response to viral pathogens, including the RLHs (RIG-l-like helicases), TLRs (toll-like receptors) and NLRs (nucleotide binding domain and leucine- rich-repeat-containing). The NLR family mediates host immunity to various pathogenic stimuli. However, in vivo evidence for NLR involvement in viral infection has not been widely explored and their involvement in RNA virus pathogenesis is controversial. This proposal seeks to explore the physiologic role of various NLRs during respiratory virus infection with influenza A virus. AIM 1: Assess the role of inflammasome and interferon-regulatory NLRs in mediating innate immune responses to influenza A virus exposure. This Aim will utilize RNA knockdown in human monocyte and human airway epithelial cell lines to assess the direct contribution of select NLRs to host defense mechanisms initiated by RNA virus exposure. AIM 2: Identify the specific influenza viral element/s responsible for NLR recognition and signal transduction. This Aim will assess the effects of viral nucleic acids, as well as, viral proteins in an effort to identify specific influenza viral components responsible for NLR recognition and signaling. AIM 3: Assess the in vivo role of NLRX1 in host immune responses following airway infection with a mouse adapted influenza A virus. The majority of NLR characterization to date has been based on data generated from human cell lines and primary mouse cells. Utilizing existing gene knockout mice, this Aim will assess the in vivo pathophysiological relevance of NLRX1 deletions to the host immune response following airway challenges with influenza A virus. Relevance: Identifying the specific cell types and the relevant NLRs within these cell types that are involved in establishing the ensuing inflammatory response following influenza virus infection would be of immense scientific and clinical value. Of particular clinical relevance, the majority of these NLR proteins contain a nucleotide binding/oligomerization domain that may be amenable to targeting by small molecule compounds. Thus, therapeutics, which activate or inhibit NLR proteins, may be used to treat a variety of infections.